1. Field of the Invention
The present invention relates to a buoy for use in loading or unloading of a flowable medium, especially oil, comprising an outer buoyancy member arranged to be introduced and secured in a submerged downwardly open receiving space in a floating vessel, and a central member rotatably mounted in the outer member, which central member is intended for anchoring to the sea bed and is arranged for passage of medium between a transfer line which, in operation, is coupled to the lower end of the central member and a tube system on the vessel.
2. Background Information
A buoy of the above-mentioned type is disclosed in the international patent application No. PCT/NO92/00056. With the buoy according to this prior application, the floating vessel, when the buoy is placed in the receiving space thereof, is rigidly attached to the outer buoyancy member of the buoy and is rotatable about the central member which is anchored to the sea bed by means of a suitable anchoring system, and the buoy itself thus constitutes a rotating body (turret). When connecting the buoy, this is pulled up into the receiving space of the vessel by a winch means on the vessel and an associated pick-up line which is connected to the submerged buoy to carry out the pulling. Thereafter the buoy is secured by means of a locking mechanism in the receiving space.
This buoy structure entails a number of substantial advantageous in relation To previously known buoy loading systems. Thus, connection and disconnection between vessel and buoy can be carried out in a simple and quick manner, even in bad weather with relatively high waves. Further, the buoy may remain connected to the vessel in all weathers, a quick disconnection being able to be carried out if a weather limitation should be exceeded.
The buoy according to the prior application broadly has a flat underside, something which results in that the buoy becomes more movement sensitive than necessary, under the influence of wave and current forces in the water. Said buoy shape also results in that the fastening points for the transfer line and for the anchoring lines of the buoy are located adjacent to the flat underside of the buoy, something which has appeared to be less favourable in practice.